Changing Bitmaps using c#

I was working on my college project where i was trying to change bit values of a Bitmap.

I am loading the bitmap to the memory stream, then extracting it to byte[] array. Now I was changing few central bits of this byte[] array and then converting it back to a bitmap image.

But i got a run time exception that "Invalid Bitmap".

Does a bitmap have some special format instead of simple bits???

Following is the code used by me:

MemoryStream mstream = new MemoryStream();
        Bitmap b = new Bitmap(@"D:\my_pic.bmp");
        b.Save(mstream, System.Drawing.Imaging.ImageFormat.Bmp);
        byte[] ba = mstream.ToArray();
        mstream.Close();

        byte[] _Buffer = null;

        System.IO.FileStream _FileStream = new System.IO.FileStream(_FileName, System.IO.FileMode.Open, System.IO.FileAccess.Read);


        System.IO.BinaryReader _BinaryReader = new System.IO.BinaryReader(_FileStream);


        long _TotalBytes = new System.IO.FileInfo(_FileName).Length;


        _Buffer = _BinaryReader.ReadBytes((Int32)_TotalBytes);

        // close file reader
        _FileStream.Close();
        _FileStream.Dispose();
        _BinaryReader.Close();
        int leng1 = ba.Length;
        int leng2=_Buffer.Length;

for(i开发者_如何学JAVA=(leng1)/2;i<leng1;i++)
{ 
 for(j=0;j<leng2;j++)
{
ba[i]=_Buffer[j];
}
if(j==(leng2-1))
{
 break;
 }
  }
   TypeConverter tc = TypeDescriptor.GetConverter(typeof(Bitmap));
   Bitmap bitmap1 = (Bitmap)tc.ConvertFrom(ba);

You must have your own goal to want to operate at this low level with a bitmap and that's fine. Unless you are performance bound it is way easier to do graphics at the graphics API level. Even if you are performance sensitive, other people have cut a path through the jungle already.

Back to the question. The BMP file format is simpler than some others but still comes in many varieties. Here is a detailed introduction to the gory details of the BMP format:

• BMP file format

Now if you are just parsing your own BMP files and you know they are 32-bit RGB, and the header is going to be such-and-such a size which you can skip over, etc, then that might work for you. If you need to handle any old BMP it gets messy real fast which is why the libraries try to take care of everything for you.